Your list of 'excuses' above are not something that I would ever say to any clients, back when I ran my business.
Jobs that look like 'problems' require talented approach, and there are no problems that cannot be surmounted, albeit the costs may be high. Explaining the scope of proposed work, and what is required for compliance with Code, and cosmetically is all part of the 'Proposal' stage of all jobs.
As to a concern over payments, spell all payments due within your contract/proposal documents. If you 'feel' that $$$$ looks like an issue, I did what Greg said.....RUN.
My approach of details and dollars, along with the suggestion to unknown clients to 'get at least three (3) estimates/proposals solved the problems of those that appeared 'shaky'.
And, yes, no matter how hard we try, I believe all of us have been 'burned' somewhat over the years.
the issue i have with just running from jobs with fear of non-payment is i see it as a little unprofessional, i'm considering your suggestion, but i'm still looking for a solution where i can be upfront about the issue